1. Field of the Invention
The present invention relates to a constant speed control method and device for a vehicle such as a motorcycle.
2. Description of the Background Art
Some vehicles, such as motorcycles are provided with a constant speed control device enabling the vehicle to operate at a constant set speed by automatically controlling an actual vehicle speed for the purpose of reducing fuel consumption, for example, by suppressing fluctuations in vehicle speed during operation on an express highway or the like.
In such a conventional constant vehicle speed control device, the set speed during the auto cruise can be changed by increasing or decreasing a vehicle speed by operation of a switch; however, as the vehicle speed is changed by a predetermined acceleration or deceleration when changing the set vehicle speed, a pleasant acceleration or deceleration feeling is not always felt by a driver or a passenger. Further, in some of the conventional constant vehicle speed operation vehicle devices, after the cruise operation is cancelled, the set vehicle speed just before cancellation of the auto cruise can be resumed by operation of the switch. A constant vehicle speed will then be started again. In this case, it is desired to smoothly resume the set vehicle speed.
Also, in a conventional constant speed control device, an actual vehicle speed is detected, and deviations between the detected actual vehicle speed and a set vehicle speed can be detected. Then, a control quantity is calculated by PD (proportional and differential) control according to the deviation. A throttle valve opening is then controlled according to the control quantity.
However, in a conventional constant vehicle speed control device, an actual acceleration cannot be detected in the constant vehicle speed control. Therefore, there is a possibility that rapid acceleration or deceleration will be generated to again cause an unpleasant feeling to the driver or passenger. Accordingly, a pleasant constant speed feeling cannot always be obtained in such prior art arrangements.